Low sound level electrical transformer



May 11, 1965 L. WRIGHT LOW SOUND LEVEL ELECTRICAL TRANSFORMER 2 Sheets-Sheet 1 Filed July 20, 1962 y 1965 Y L. L. WRIGHT 3,183,463

LOW SOUND LEVEL ELECTRICAL TRANSFORMER Filed July 20, 1962 2 Sheets-Sheet 2 United States Patent 3,183, ld3 LGW SOUND LEVEL ELECTRHCAL TRANSFQRMER Leonard L. Wright, Sharon, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa a corporation at Pennsylvania Filed July Ed, 1962, Ser. No. 211,278 7 (Claims. (Cl. ass-95) This invention relates in general to electrical apparatus and more particularly to electrical inductive apparatus having low sound levels.

There has developed a need for electrical inductive apparatus having extremely low air-borne and structureborne sound levels. This need is particularly acute in the military for marine use. Not only must the device have low sound production characteristics, but it must be able to withstand high shock levels. The requirement of high shock capability makes impractical the present methods of construction and mounting used to reduce the sound levels in electrical inductive apparatus.

Accordingly, it is a general object of this invention to provide a new and improved electrical apparatus having low sound levels.

it is a more particular object of this invention to provide a new and improved electrical inductive apparatus having low air-borne and structure-borne sound levels.

Another object of this invention is to provide a new and improved electrical apparatus, such as a transformer, that is capable of withstanding high shock levels.

Briefly, the present invention accomplishes the above cited objects by providing electrical inductive apparatus utilizing a double suspension system. More specifically, the electrical inductive apparatus embodies a magnetic core suspended within an enclosure or casing by a suita le insulating medium, with electrical windings wound around the enclosure. The magnetic core and winding assembly is then suspended within a container or tank by an insulating system comprising a mixture of cured thermosetting resin and finely divided inorganic fillers. This double suspension system not only reduces the sound level of the inductive device, but it provides an electrical apparatus having superior resistance to shock.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

FIGURE 1 is a top plan view, partly in section illustrating a transformer constructed in accordance with this invention;

PEG. 2 is a view in front elevation, partly in section of the transformer shown in FIG. 1;

FIG. 3 shows a magnetic core and its enclosure that may be used in the transformer shown in FIGS. 1 and 2;

FIG. 4 shows another enclosure that may be used in the transformer shown in FIGS. 1 and 2; and

5 is a top plan view illustrating the directions of vibration pick-up used to obtain vibration-borne noise measurements on a conventional low noise transformer and a low noise transformer constructed according to the teachings of this invention.

Referring now to the drawings and FIGS. 1 and 2 in particular, there is illustrated an inductive device, specially a transformer it), constructed in accordance with the teachings of this invention. In general, the transformer includes an enclosure or tank 12, formed of metal or other suitable material, having disposed therein a core and coil assembly. Specifically, the core and coil assembly comprises the magnetic core id disposed within an enclosure or casing id and suspended within enclosure 18 by a suitable highly viscous insulating medium 20. Primary and secondary windings l5 and 16 are inductively disposed on the enclosure 13 which surrounds the magnetic core lid. The space between the windings 15 and lo and the transformer tank 32 is filled with an insulating material 211, by means of which the heat generated in the windings l6 and the core 14 is conducted to the transformer tank 12.

In particular, the tank 12 includes a top portion or cover 2 and a bottom portion or member 26 which are secured to the walls of the tank 32 by suitable means such as welding or screws (not shown). The tank 12 also ineludes one or more mounting brackets 28 which are secured to the tank 12 by suitable means, such as welding.

The tank 12. is also provided with conventional knockouts or conduit openings Ell to permit passage of electrical connections into the tank 12.

The magnetic core 1 is formed of a suitable magnetic material. The usual method of forming magnetic core id consists of winding a thin sheet of the magnetic material into a toroidal core. However, it is obvious that other types of cores could be employed, such as the stacked laminated type. Thereafter, the wound toroidal core is placed within an enclosure 18 in the shape of a toroidal box having dimensions slightly larger than the magnetic core 14-. The magnetic core 14 is freely disposed within the enclosure lit, with a clearance between all surfaces of the magnetic core 14 and the enclosure ill. This clearance between the magnetic core 11 and the en.- closure 13 is continuously maintained by filling the euclosure with a highly viscous insulating substance 2 1 The enclosure is then sealed, thereby resulting in a core that is completely isolated from its enclosure, highly resistant to shock, and producing a minimum of sound.

More specifically, as shown in FIG. 3, magnetic core enclosure has a trough-like cross-section having a bottom wall 32, a vertical inside wall 34, and a vertical outside wall 36, forming an annular chamber, within which is disposed the magnetic core 14. The toroidal trough enclosure 18, with the magnetic core Ild therein, is covered with member 38 which has inside wall 33 and outside wall 35, with said walls fitting over the upper edges of walls 34 and 36, respectively. An adhesive 37 or other suitable fastening means is used to hold the cover 38 in place and seal the enclosure 18, after the insulating medium Eli and magnetic core are suitably disposed within the enclosure 18. It will be appreciated that other shapes of enclosures and magnetic cores may be employed than those shown. For example, the enclosure may be constructed as shown in FIG. 4, utilizing concentric tubes and upper and lower enclosing members. More specifically, the enclosure shown in FIG. 4 is constructed of an inner hollow cylinder or tube 5t an outer concentric hollow cylinder or tube 52, a lower or bottom enclosing member and an upper or top enclosing rrember 56.

The enclosure may be formed of non-magnetic metals or insulating materials having suificient strength. For example, insulating materials that would be suitable are the laminated resinous materials prepared from thermoplastic or-thcrmoset resins such as eth'l cellulose, cellulose acetate, melamine resins and the like. Nylon molding composition is also satisfactory. if non-mag netic metals are used to form the enclosure 18 shown in 3, the metal cover 33 should be insulated from the walls and 36 of the enclosure l3. For example, an aluminum enclosure in having an anodized coating would be suitable. The insulating coating 37 between the walls 33 and of cover 38 and the walls 34 and 36 of the enclosure 13 is necessary to prevent a complete meta-iii path around the magnetic core "a l, which would ansasee allow currents to circulate around the enclosure 18 and also reduce the effect of the magnetic core 14. Also, the bottom 32 and the walls 3d and 36 of the enclosure 13 may be formed of a non-magnetic metal and the cover 38 may be formed of an insulating material. In like manner, if non-magnetic metals are used to form the enclosure 18 shown in FIG. 4, the top member 56 or the bottom member 54, or both, should be insulated from inner wall or tube and outer wall or tube 52. Also, the inner and outer tubes, 5d and 52, may be formed of insulating materials and the enclosing members, 54 and 56, may be formed of non-magnetic metals. Or, the inner and outer tubes, 5t) and 52, may be formed of non-magnetic metals and the upper and lower enclosing members, 55 and 5%, may be formed of insulating materials.

The insulating medium as may be any highly viscous material having good insulating qualities that is capable of suspending the magnetic core 14 within the enclosure 18. For example, liq id, predominantly linear, phenyl methyl vinyl siloxane, of which t e vinyl group is a relatively small proportion, cross-linked by applying a suitable cross-linking catalyst, such as the platinum compound platinic chloride, has been found to be highly satisfactory. This insulating material is poured as a iquid, filling all voids and then forms a heat stable resilient mass. Before the core 14 is introduced into the enclosure 13, a small quantity of insulating material 2t) may be poured into the enclosure. When said material forms a resilient mass, the core 14 is suitably disposed within the casing with said material spacing the core 14 from the bottom 32 of the enclosure 18. Then the enclosure may be filled with insulating material 2d so that the core 1a is completely surrounded with said insulating material.

Referring again to FIGS. 1 and 2, the primary and secondary windings 15 and 15 are disposed in an inductive relationship with the encased magnetic core 14. FIGS. 1 and 2 show a first set of windings 15 wound around enclosure 18 and a second set of windings 16 wound around the first set of windings 15. If the enclosure 18 is formed of a non-magnetic metal, additional in sulation material it) may be placed between the set of windings 15 and the enclosure 18. N 0 additional insulating substance will be required if the enclosure 18 is formed of an insulating material. Additional insulating material 42 may be placed between the two sets of windings 15 and 16. These winding relationships are shown by way of ilustration only, and are not meant to limit the invention in any way.

The magnetic core 14, suitably disposed within the enclosure 13 which is filled with the ighly viscous insuating medium 29 and which has the windings 15 and 16 suitably disposed relative to the enclosure 18, is suspended within the enclosure or tank 12 and the insulating material 22 is added to the tank. in general, the insulating material 22 comprises a mixture of certain types of solventless thermosetting resins, such as those of the epoxy type, the polyester type or the silicone type and certain finely divided, inorganic, non-friable, inert fillers. The fillers comprise at least one filler selected from the group consisting of silica, silicates, alumina, and hydrated alumina. Plasticizers may be added to the resins to provide for more elastic products.

The resins employed in the mixture which forms the insulating material 22 are converted or cured to a thermosetting state or condition as described hereinafter. The insulating material then forms a solid mass with the enclosure 18 and windings 15 and 16. The bonding action between the insulating material 22 and the enclosure 18 and windings 15 and 16, and the bonding action between the insulating material 22 and the transformer tank 12 serves to support and suspend said enclosure and windings within the tank 12.

The method of forming this second suspension system comprises positioning and suspending the encased core 14 and windings 1S and 16 within the tank 12 so that there is suitable clearance between the tank 12 and all parts of said encased core and winding assembly. A suitable liquid resin of one of the types previously mentioned, having a low viscosity, is introduced into the tank 12. to a predetermined level. Thereafter, finely divided inorganic filler is introduced into the tank 12 until the level of the mixture reaches another predetermined level. The tank 12 may be vibrated until the resin appears to have substantially filled all open spaces or voids in the assembly comprising the encased core 14 and windings 15 and 16. During the vibrating of the tank 12, after the voids appear to have been filled, the balance of the fi ler is added until the final level of the mixture is reached. The potted transformer 19 is then placed in an oven or heating device, or current is passed through the unit to bring it to a predetermined temperature and for a period of time sufficient to cure the insulating material 22 to a tough, hard solid.

it is to be understood that other means may be employed for compacting the mixture of resin and filler which makes up the insulating material 2.2, such as placing the tank 12 under vacuum to remove all air from around the particles of the filler to ensure complete filling of the space around the encased core 14 and windings 15 and 16. It is also to be understood that other means may be employed for converting the thermosetting resin to a thermosetting state. It has been found that a thermosetting resin of the epoxy type may be cured by placing the transformer 1a? in an air circulating oven for approximately three hours at C. Other methods of curing or polymerizing the thermosetting resin may be employed in a particular application, such as subjecting the resin to certain types of radiation.

As shown in FIGS. 1 and 2, the double suspension construction of transformer 10, comprising the suspension of the magnetic core 14 within the casing or enclosure 18 and the suspension of the assembly comprising said encased core and windings within the transformer tank 12, produces a rugged, shock resistant unit that creates a minimum of air-borne and vibration-borne sound levels.

The reduction in air-borne and structureborne sound levels is shown in the following tables. These tables compare a transformer constructed according to the teachings of this invention with a transformer of comparable rating which is currently used when low sound levels are required. The conventional transformer has a shell form core constructed of I plate punchings and is mounted in a casing, along with the windings, on a bracket. Air is used to insulate the core and windings from the outer casing.

Table No. 1 compares the airborne sound levels of a conventional low noise transformer with the airborne sound levels of a transformer constructed according to the teachings of this invention. The noise levels were measured in bands and Table No. 1 charts the peak db for each band or range of noise frequencies.

Table No. 1.--Airb0rne noise levels Conventional Double Suspen- Noise Frequency (Cycles Per Second) Low Noise sion Type Transformer Transformer (Peak Db) (Peak Db) 4O 42 (i2 28. 5 57 2G 49 15 Table No. 2 compares the structure-borne sound levels of a conventional low noise transformer with the structureborne sound levels of a transformer constructed according to the teachings of this invention. The noise levels are given in velocity decibels D A velocity decibel is determined by the following formula:

Velocity cm./sec. era/sec.

bv ll) Table No. 2.-Structure-b0rne sound levels Double Suspension Trans- Type Transformer former Db at 800 c.p.s.

Conventional Dbv at 400 e.p.s.

Position on Transformer D at 400 c.p.s.

D at 800 c.p.s.

The apparatus embodying the teachings of this invention has several advantages. For example, the use of the insulating material in the construction disclosed provides increased resistance to corrosion and contamination by dust and gases, and permits a reduction in the electrical clearances required compared to a conventional transformer of the same general type. The reduced clearances resulting from the construction disclosed permits reductions in the size and Weight of the core and coil assemblies included in a transformer as previously described.

Further, there has been disclosed an electrical inductive device that will generate reduced air-borne and structureborne sound levels. Also, the double suspension construction employed produces a device that will not be adversely afiected when subjected to high shock levels.

Since numerous changes may be made in the above described apparatus and diiferent embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. Electrical inductive apparatus comprising, a magnetic core, a first enclosure, said magnetic core being disposed in said first enclosure, said first enclosure being filled with a first insulating and sound dampening means to completely surround said magnetic core and separate it from said first enclosure, electrical windings, said electrical windings being disposed in inductive relation with said enclosed core, a second enclosure, said enclosed core and electrical windings being disposed in said second enclosure, and second insulating and sound dampening means, said second insulating and sound dampening means substantially filling said second enclosure to embed and completely suspend said enclosed core and electrical windings in said second enclosure.

2. An electrical inductive device comprising a first enclosure being substantially filled with a highly viscous insulating and sound dampening substance, a magnetic core, said magnetic core being disposed in said first enclosure and being completely surrounded with said highly viscous substance to prevent contact between said magnetic core and said first enclosure, said first enclosure being constructed to provide an open electrical circuit around said magnetic core in a transverse direction, electrical windings, said electrical windings being disposed in inductive relation with said enclosed magnetic core, a second enclosure, said enclosed magnetic core and electrical windings being disposed in said second enclosure, and insulating and sound dampening material, said insulating and sound dampening material substantially filling said second enclosure to prevent contact between said enclosed magnetic core and electrical windings and said second enclosure, said insulating a-nd sound dampening material comprising a mixture of finely divided, inorganic, nonfriable, inert filler and cured thermosetting resin.

3. Electrical inductive apparatus comprising, a casing being substantially filled with a gelatinous form of silica, a magnetic core, said magnetic core being disposed in said casing and being completely surrounded with said gelatinous form of silica, said casing being formed of a plurality of members of which at least one member is electrically non-conductive, electrical windings, said electrical windings being disposed in inductive relation with said encased magnetic core, an enclosure, said encased magnetic core and electrical windings being suspended in said enclosure, and insulating and sound dampening material, said insulating and sound dampening material filling the space between the encased magnetic core and electrical windings and said enclosure to completely capsulate said magnetic core and electrical windings and isolate said magnetic core and electrical windings from said enclosure, said insulating and sound dampening material comprising a mixture of finely divided, inorganic, non-friable, inert filler and cured thermosetting resin.

4. A 400 cycle transformer comprising an inner en closure being substantially filled with an insulating material comprising phenyl methyl vinyl siloxane crosslinked by a suitable cross-linking catalyst, a magnetic core, said magnetic core being disposed in said inner enclosure and being completely surrounded with said insulating material, said inner enclosure being constructed to provide an open electrical circuit around said magnetic core, electrical windings, said electrical windings being in inductive relation with said enclosed magnetic core assembly, an outer enclosure, said enclosed magnetic core assembly and electrical windings being disposed in said outer enclosure, and insulating material, said insulating material capsulating said enclosed magnetic core and electrical winding assembly to completely isolate said assembly from said outer enclosure, said insulating material comprising a mixture of finely divided, inorganic, nonfriable, inert filler and cured thermosetting resin.

5. An electrical inductive device comprising a first enclosure being substantially filled with a colloidal form of silica, a magnetic core, said magnetic core being disposed within said first enclosure and being completely surrounded with said colloidal form of silica, said first enclosure being formed of a plurality of metal members, said metal members having an insulating coating thereon disposed to provide an open circuit around said magnetic core when said metal members are assembled, electrical windings, said electrical windings being disposed in inductive relation with said enclosed magnetic core, a second enclosure, said enclosed magnetic core and electrical windings being suspended in said second enclosure, and insulating material, said insulating material filling the space between the enclosed magnetic core and electrical Windings and said second enclosure to completely isolate said magnetic core and electrical windings from said second enclosure, said insulating material comprising a mixture of finely divided, inorganic, non-friable, inert filler and cured thermosetting resin.

6. A low noise level transformer comprising, a first and second suspension system, said first suspension system comprising a first enclosure being substantially filled with a gelatinous insulating substance, said first enclosure being formed of non-magnetic metallic members having an anodized coating thereon, a magnetic core, said magnetic cdre being disposed in said first enclosure and being completely surrounded with said gelatinous substance to prevent contact between said magnetic core and said first enclosure, electrical windings, said electrical winding? being disposed in inductive relation with said enclosed magnetic core, said second suspension system comprising a second enclosure with said enclosed magnetic core and electrical windings being disposed in said second enclosure, and insulating material, said insulating material substantially filling said second enclosure to prevent contact between said enclosed magnetic core and electrical windings and said second enclosure.

7. A low noise level transformer comprising, a first and second suspension system, said first suspension system comprising a magnetic core assembly having a casing substantially filled with highly viscous first insulating means, said casing being formed of an insulating material, a magnetic core, said magnetic core being disposed in said casing and suspended in said first insulating means, electrical windings said electrical windings being disposed in inductive relation with said magnetic core assembly, said second suspension system comprising a tank with said electrical windings and magnetic core assembly being disposed in said tank, second insulating means, said second insulating means substantially filling said tank to a predetermined level to embed and encapsulate said electrical windings and magnetic core assembly, the sole mechanical connection between said electrical windings and magnetic core assembly and said tank being the bond between said second insulating means and said electrical windings and magnetic core assembly and between said second insulating means and said tank, said second insulating means comprising a mixture of finely divided, inorganic, non-friable, inert filler and cured thermosetting resin.

References Cited by the Examiner UNITED STATES PATENTS 366,544 7/87 Westinghouse 336-94 1,116,020 11/14 Colpitts 336-96 X 1,130,260 3/15 Dann 336-90 1,862,503 6/32 Cadieux 336-96 2,313,379 3/43 Wood 336-100 X 2,422,591 6/47 Sigmund et al. 336-100 2,460,795 2/49 Warrick 336-96 X 2,743,308 4/56 Beadsley 336-96 X 2,909,741 10/59 Arntzen et al. 336-100 2,946,973 7/60 Lufcy 336-90 X 3,018,455 1/62 Brandon et al. 336-100 3,030,597 4/62 Piaia et al. 336-96 X 3,106,769 10/63 Goethe et al. 336-96 X JOHN F. BURNS, Primary Examiner. 

1. ELECTRICAL INDUCTIVE APPARATUS COMPRISING, A MAGNETIC CORE, A FIRST ENCLOSURE, SAID MAGNETIC CORE BEING DISPOSED IN SAID FIRST ENCLOSURE, SAID FIRST ENCLOSURE BEING FILLED WITH A FIRST INSULATING AND SOUND DAMPENING MEANS TO COMPLETELY SURROUND SAID MAGNETIC CORE AND SEPARATE IT FROM SAID FIRST ENCLOSURE, ELECTRIC WINDINGS, SAID ELECTRICAL WINDINGS BEING DISPOSED IN INDUCTIVE RELATION WITH SAID ENCLOSED CORE, A SECOND ENCLOSURE, SAID ENCLOSED CORE 